Bearings take on a tough sawmill assignment
09 June 2013
The Belgian Industrie du Bois Vielsalm (IBV) Group operates six sawmill lines with an aggregate daily processing capacity of 6,000 cubic metres of softwood.
IBV is among the leading softwood sawmills in the Benelux region and one of the top 20 producers in Europe. It is also a major supplier of pellets, a useful combustible by-product of its waste streams.
Pellet production is tough on bearings. The process involves pulverizing wood debris into a dough-like consistency. In this state, the material is pushed by two friction rollers through the holes of a perforated drum where the pulp is extruded to create the pellets.
Challenged by the heavy loads, impacts and vibration associated with this process, the original bearings used by IBV in their pellet mill equipment needed to be replaced about every 500 hours. This frequent and costly downtime prompted IBV to approach its supplier, Luxembourg based Brammer, with a request to seek an alternative, more durable bearing product.
Brammer arranged an analysis of the entire production process by Timken engineers who subsequently solved the problem by specifying their two-row spherical roller bearings. Now installed, these bearings have a life of around 2,500 hours some five times that of the original bearings. Moreover, the Timken bearings run about five to eight percent cooler than the competitor bearings, prolonging lubricant life and contributing to their extended life in this application.
“Timken spherical bearings have substantially reduced our operating costs and increased our productivity,” says IBV’s pellet production manager, Bruno Simon. “Now our mills can operate much longer without interruption.” Today, IBV insists on Timken bearings for the rollers on four of its pellet mills that produce a total of around 150,000 metric tons of pellets annually.
Inspired by its tapered roller bearing, Timken's redesigned, high power density spherical roller bearing enables OEMs to downsize their designs while improving performance. And for users, the new design can mean less maintenance, while cooler operating temperatures help to lengthen bearing service life.
The bearings feature either stamped steel, window-type cages or precision-machined, roller-riding brass cages. They come in a wide variety of sizes (from 25mm bore to an outside diameter of 2,000mm) and configurations.
The nitrided, stamped steel slotted cage helps provide better purging of contaminants, and the optimised internal geometries provide positive axial roller guidance and improved lubricant distribution. Meanwhile, the circumferential roller guidance generates positive hydrodynamic contact, contributing to better roller/cage interaction.
The result of these innovations is an 18 percent increase in capacity for a claimed 75 percent design life improvement over Timken's previous spherical roller bearing design.
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